The IP Multi-Media Subsystem (IMS) is an IP multimedia and telephony core network. It is defined by 3GPP and 3GPP2 standards and organizations based on IETF Internet protocols. IMS is access independent as it supports IP to IP session over wireline IP, 802.11, 802.15, CDMA, packet data along with GSM/EDGE/UMTS and other packet data applications. IMS is standardized reference architecture. IMS consists of session control, connection control and an applications services framework along with subscriber and services data. It enables new converged voice and data services, while allowing for the interoperability of these converged services between subscribers. IMS network infrastructure enables the convergence of data, speech, and mobile network technologies over an IP-based infrastructure.
Designed to fill the gap between existing traditional telecommunications technologies and the Internet, IMS provides the key functionalities required to enable new IP services via mobile networks taking into account the complexity of multimedia, constraints of the underlying network, managing mobility and the multitude of emerging applications. IMS permits and enhances real time, multimedia mobile services such as rich voice, video telephony, messaging, conferencing and push services by responding to the emerging trend to move toward a common, standardized subsystem. IMS services may include Push-to-Talk-over-Cellular, real time video sharing, interactive gaming, Instant Messaging Services, voice messaging, voice and video telephony, and video-conferencing.
Quality of service is commonly defined as the service users' degree of satisfaction during a given communications session. Consistently anticipating and meeting users' quality of service needs is what distinguishes successful communications service and product providers from their competition.
Network Services are considered end-to-end, this means from a Terminal Equipment (TE) to another TE. An End-to-End Service may have a certain Quality of Service (QoS), which is provided for the user of a network service. It is the user that decides whether he is satisfied with the provided QoS or not.
To realize a certain network QoS, a bearer service with clearly defined characteristics and functionality is to be set up from the source to the destination of a service. The bearer service includes all aspects to enable the provision of a contracted QoS. These aspects are among others the control signaling, user plane transport and QoS management functionality. A bearer service layered architecture may be used where each bearer service on a specific layer offers its individual services using services provided by the layers below.
Cellular telephony networks today are introducing higher bandwidth technologies in the access. Combined with higher access speeds, the core network is moving to using packet-based connectionless transports for services. With the advent of the IP Multimedia Subsystem (IMS), home based service control for multimedia applications is becoming a reality. Voice over IP (VoIP) and other QoS sensitive multimedia applications are being deployed and thus there is a new need for these applications to be able to manage their QoS needs.
In particular, known policy control from an application is supportable in a roaming configuration while preserving home-based service control. It is a drawback of the known systems that bearers are required to traverse the home network.
Thus, a need exists for policy control from an application that may be supported in a roaming configuration while preserving the home based service control and not requiring bearers to traverse the home network.